Mirror coated sunglass lenses are widely used in the sunglass industry. Mirror coatings are useful for filtering light as well as creating a fashionable appearance. Conventional mirror coated lenses are created by applying, to the convex side of a conventional tinted lens, a very thin reflective material. The technique of applying the mirror is called vacuum deposition. Thickness of the reflective film is in the order of microns. Depending on the thickness and type of the reflective material, the reflective film will reflect a portion of the total amount of light striking the surface of the reflective film and allow the remaining portion of light to pass through. The drawback to lenses that have reflective coatings is that the reflective coatings are very susceptible to abrasion, scratching and visible smudging, depending on the type of reflective coating some are more susceptible than others. Mirror coated lenses that have smudges on them tend to be somewhat difficult to clean and are easily scratched and/or abraded when trying to remove smudges from the surface of said reflective film. Again, depending on the type of reflective coating, some are more susceptible than others.
There are basically two types of scratch resistant coatings that are applied to eyeglass lenses. The first type is applied by vacuum deposition and typically consists of metal or silicon type material. Most all vacuum deposited mirror coated lenses are provided, during the coating process, an outer coating (of the type mentioned) which provides limited scratch protection. Without it, the reflective medium would be overly susceptible to abrasion. The other is a polymer/resin type coating that is applied to the surface of an uncoated eyeglass lens (in liquid form) and then cured to a very hard solid state by exposure to ultra-violet (UV) light and/or heat. The cured polymer coating then provides a very durable scratch resistant outer surface. Of the two basic types of protective coatings, the polymer/resin type coating is considerably more durable.
There are numerous types of polymer type scratch resistant coating products available for "uncoated" plastic eyeglass lenses and there are many patents covering the numerous types. Polymer coatings, however, are designed to be applied directly to the surface of a plastic lens, not to the reflective surface of a mirrored lens. When applied to the surface of a mirror coating in the manner in which they are applied to uncoated lenses, the polymer coatings do not adhere.
Typically, all polycarbonate lenses have polymer type scratch resistant coatings. Both front and back coatings can be applied in different ways such as dip coating or spin coating. If a mirror coating is desired, the mirror coating is placed over the scratch resistant coating. The very thin reflective medium is then the outermost layer. Allyl diglycol carbonate (CR-39) is another type of plastic commonly used in the optical industry. Though much more scratch resistant than polycarbonate, manufacturers often apply polymer type scratch resistant coatings to CR-39 lenses as well. Again, if a mirror coating is desired, the mirror coating is placed over the scratch resistant coating. The very thin reflective medium is then the outermost layer.
The present invention discloses not only the idea of applying a polymer type protective coating over the surface of a mirrored sunglass lens but a means of accomplishing said objective using conventional polymer type scratch resistant coatings. Applying a polymer type scratch resistant coating to the reflective surface of a mirrored lens will provide the same level of protection to the reflective surface as is presently provided by such polymer coatings for non-mirrored lenses. Additional protection afforded by the polymer coating includes reduced sensitivity to liquids such as sweat, oil from skin etc. which tend to smudge and discolor the appearance of an unprotected mirror surface. Along with such enhanced protection, the invention provides the option of adding color to the protective coating for the purpose of additional filtering of light and for the enhancement of the aesthetic appearance of the mirror.
These benefits are achieved by means of a relatively thin layer of protective coating that does not produce any noticeable degree of double reflection.